/Engine/Plugins/Runtime/GameplayAbilities/Source/GameplayAbilities/Public/GameplayEffect.h
Returns the custom magnitude calculation class, if any, for this magnitude. Only applies to CustomMagnitudes
[TSubclassOf](API\Runtime\CoreUObject\Templates\TSubclassOf)< [UGameplayModMagnitudeCalculation](API\Plugins\GameplayAbilities\UGameplayModMagnitudeCalculation) > GetCustomMagnitudeCalculationClass() const